Rheostat



June 22 1926., I, 1,589,501

M. J. WOHL RHEOSTAT Filed May. 26. 1925 amvawto'c f. ag waum w Patented June 22, 1926.

UNITED STATES PATENT OFFICE- MAURICE J. WOHJJ. F LONG ISLAND CITY, NEW YORK, ASSIGNOR TO HARRY HERTZ- BERG, OF BROOKLYN, NEW YORK.

RHEOSTAT.

Application filed May 26, 1925. Serial No. 32,942.

This invention relates to improvements in rheostats, particularly rheostats to be used for current regulation in radio systems, and it is the principal object of the invention to provide a rheostat allowing a gradual and uniform adjustment for compensating automatically for differences in battery voltage. The known devices of this kind have a resistance which is fixed at a certain voltage, or in other words, do, for instance, allow an adjustment of a six'ohm device but not an adjustment for regulating near ten ohms. It is the object of the present invention to overcome this disadvantage by using a resistance material, having a high temperature coefiicient and arranging the same in a novel and improved manner. I I

Another object of he invention is the provision of an adjustable rheostat having a highlyresisting metal strip wound about the threads of a plug in an improved and novel manner, and mounting the same to the socket of a radio tube in a novel and improved manner. j

A further object of the invention is the provision of a rheostat for radio tubes allowing a novel panel mounting adapted to be operated by a knob. I

A still further object of the invention is the provision of a rheostat allowing a gradua1 adjustment giving uniform variations'and not a step-by-step variation, as in the known devices, and one which eliminates the use of ernier or graduated scales.

These and other objects and advantages of my novel rheostat will become more fully known'as the description thereof proceeds, and will then be specifically defined in the appended claims.

In the accompanying drawing, forming a material part of this disclosure Fig. 1 is a sectional side elevation .of a rheostat constructed according to the present invention, attached'to a tube socket shown in broken lines. j

Fig. 2 is a front elevation of the rheostat. Fig. 3 is a side elevation illustrating the panel mounting. j j

I F'g. 4 "s a section online 44 of Figure 1.-

.Fig. 5 a 'sectionf'on" line of Fig,-

rent through the 'rheostat. swarm-t eatises wee be e Fig. 6. is diagram. of the passage of ar I.

present invention, comprises a tubular socket -of insulating material having contact strlps 11 and 12 mounted thereon, on its outer side, diametrically opposite to each other. The upper angularly bent ends 11 and 12 of these strips form contact fingers which rest in recesses 13, in the upper edge of the socket, while their lower ends are held by screws 1e and 15 to the socket, and are angularly bent, as at 16 and 17, and at their extreme ends are adapted to be attached to the binding posts 18, for instance, of a tube socket 19, illustrated in broken lines in Figure 1.

The rheostat has the'form of a hollow cylmdrical plug 20 equipped with an operatlng knob 21, knurled at its outer face. The plug has a double fiat thread on its cylindrical'surface, and a wire strip 22 of a resistance material having preferably a high temperature coefficient, is wound about the plug within the two helical grooves formed by the threads. This strip ofresistance material is guided through openings 23 in the plug crossing the interior thereof as at 24, while its ends 25 and 26, extend into the hollow interior of the plug, through openings in the side walls near the bottom of the plug.

The bent end 11 of stri 11 forms a con tact with the flat wire lying in one of the two helical grooves of the double fiat thread, and the other bent end 12 forms a contact with the flat wire in the second groove. The two ends 11 and 12 form the nut for the threaded plug, and by screwing the plug more or less into the socket, more or less of the flat wire is inserted into the circuit between the prongs 11 and 12*. Those parts of the flat strips of wire from 11 to 25 and 12 to 26 remain out of the circuit as may be seen from diagram Figure 6. It is well known, that by using a resistance material having ahigh temperature coefficient the min rent supply to a radio tube may be kept constant while the voltage varies. Devices which accomplish this, are made in different fixed resistance values. This device hasthe added advantages that the resistance may' bevari'ed to best current value of a. tube at normalbatthe current constant. a t? sates se s 9 e t e h flidelleeistancem on the socket is also an advantage gained by this invention, particularly for radio tubes which need little adjustment. It saves considerable space on the panel and makes the set foolproof.

In Figure 3 is shown how the same rheostat may be mounted upon the panel 34 ot' a radio set. The panel mounting 27 con sisting of a plate of insulating material, carries the socket 10 by means of screws 28 and 29, to which the ends of contact stops 16 and 17 and connecting wires are secured. This plate is fastened by means of suitable screws 35 to panel 34. A pin 30 has attached thereto at the front an operating knob 31, and extends through panel 34 and panel mounting 27, socket 10, plug 20 and square opening 32 in knob 21 of plug 20, into which this pin fits by a square formed thereon. The pin carries a nut 33 at its outer end to .hold it in place.

The turningoi the knob 31 screws the plug part of the rheostat more or less into the socket which varies the resistance as before described. This form of my invention is intended to be used for radio tubes which use a more frequent adjustment, in which case I use, preferably a fiat wire of high resistance and normal temperature coeflicient.

The operation of my improved rheostat will be entirely clear from the above description and without further explanation; it will be understood that by the rotation of the plug a gradual adjustment giving uniform variation and not a variation in little steps which the usual rheostat provides, will be effected.

It will be understood that such changes may be made in the construction and in the general arrangement of my improved rheostat, as fall within the scope of the appended claims, without departure from the spirit and principle involved.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent is: p

1. A rheostat comprising a socket, ter minals thereon adapted to hold the conductors of an electric circuit..a threaded plug in engagement with said socket, a resistance element wound into the threads of said plug and meanson said socketto vary the, resistance of said element between said terminals by rotating said plug.

2. A ah'eostat comprising a plug, a re sistanc el wire forming a-helix on the outside nfsaid plug. a. holder I p p for said: plug means on saidholder to form electric contacts v re-atdifienent points thereotto vajy {the esistance between said pointsby rotating said plug in its holder. 3. A rheostat comprising a -plu g,..a thread von said plug, an. electric conductor wound into the grooves of said threatlelectrically connected to one terminal of an electric circuit, a socket for said plug, a contact finger on said socket adapted to engage said conductor and to form a connection with the other terminal of said circuit.

4. A rheostat comprising a screw having a double thread of insulating material, a band of resistance material in each of the two grooves of said thread, said bands being joined at one end of said screw and open at the other end; a finger for each band forming a contact therewith, a support for said fingers, and means for operating said screw to vary the length of the hand between said fingers.

5. A rheostat comprising a plug and an operating knob, a double thread on said plug, a metal strip wound about the threads of said plug, a socket for said plug, a pair of contact lingers on said socket adapted to engage said metal strip in dillerent grooves of said thread for gradually and uniformly varying the resistance in an electric circuit.

6. A rheostat comprising a plug of insulating material having a double thread on its outer side, a metal strip having a high resistance coeflicientguided and located in the grooves formed by said double thread, passing from one side of said plug to the other side near the top of said plug and having lower dead ends, a pair of contact stops engaging said metal strip within different threads of said plug, said contact stops being adapted to be attached to a tube socket, and a knob for operating said plug to gradually and uniformly vary the re sistance in an electric circuit,

7. A vrheostat comprising a plug having a thread, a resistance element wound about said plug following said thread, a socket for .said plug having terminals to hold the conductors of an electric circuit, a panel to which said socket is attached, means pass-- ing through said panel being attached to said plug for rotating of the Same from the outside of said panel, and means on said socketengaging said resistance element for gradually anduniformly varying the resistance of said element between said terminals by rotatingsaid plug.

8. A rheostat for radio apparatus conr prising a socket, contact strips resting with their upper angular ends in differentrecesses of said socket, a plug having a double thread adapted to be engaged into said socket, a metal strip. of. a high resistance coefiici'ont guided in the double thread. adapted tobe engaged by said. angular ends for allowing an automatic and gradual coi'n'pem eating. for differences in battery'voltage, a radio panel, means for mounting said s'oker on onesiderotsaid panel, and. a means on the other side of said. panel. for allowing a ,regulation trom. the outside. thereof, 9, A; rheostat comprlslng' a screw, a band.

of resistance material lying in the groove of said screw, electrically connected to one terminal of a circuit, a nut for said screw, an electric contact finger engaging said band forming part of said nut and means on said contact finger to form an electric c0n-- nection with the other terminal of said cir-- cuit and to support said rheostat on said terminal.

Signed at Long Island City in the county 10 of Queens and State of New York this twenty-first day of May A. D. 1925.

MAURICE J. VVOHL. 

